Fish in the aquarium

A beautiful, well-functioning aquarium is an ornament to any living room! But even a fish cellar with many rather practical breeding tanks can have that certain something. Here you can find out what you need for successful fish keeping in an aquarium and how to keep your fish as species-appropriate as possible.

What do I have to consider for a fish aquarium?

In a fish aquarium, the fish are the main focus. Unlike in aquascapes or planted aquariums, in a fish tank the fish are not just a nice accessory, they play the main role!

It is important that you set up the aquarium for your ornamental fish in such a way that the fish can feel comfortable in it. The aquarium setup must be species-appropriate and oriented towards the needs of the aquarium fish.

Choose the right aquarium size

Data sheets on aquarium fish often show widely differing size specifications with regard to the edge length of the aquarium. If in doubt, always opt for the larger aquarium size - even a 200 litre glass tank is simply tiny compared to a river or lake. Let's give our fish as much space as possible!

The exception here is very small fish or juvenile fish that practically have to stand in the food so that they don't starve to death. A large aquarium is far too big here, the animals would suffer from hunger and degrade severely. A smaller tank may be justified here.

In a community aquarium with several fish, the following applies: The fish that needs the largest aquarium determines the aquarium size.

Aquarium fish that are kept in tanks that are too small tend to become stunted: their bodies remain smaller and can sometimes even appear crippled, while their organs reach their original size and the fish then suffocates itself, so to speak. You should avoid this at all costs!

What aquarium equipment is absolutely necessary?

Nowadays there is a wide range of aquarium equipment available. What technology is absolutely necessary in a fish aquarium, especially for beginners?

Filtration

In the aquarium filter, suspended matter is filtered out of the aquarium water, and important filter bacteria take care of removing pollutants from the water. A fish aquarium cannot do without a filter, especially in more heavily stocked tanks.

In our article "Internal filter vs. external filter" we explain the different types of filters and help you decide which type is best suited for your aquarium project.

Heater

Depending on the origin of your aquarium fish, they need a correspondingly high water temperature in the aquarium. Many ornamental fish feel comfortable at about 25 °C, but there are exceptions upwards or downwards. Fish from temperate and subtropical climates are happy in the aquarium at a normal room temperature of 18 to 25 °C; fish from the tropics usually need it a little warmer.

Make sure that you buy an aquarium heater that is slightly undersized. The less often the heater has to switch on and off in the aquarium, the less prone it is to faults.

You can read all about choosing the right aquarium heater in our blog Aquarium heating and temperature monitoring.

Light

Fish per se do not necessarily need light to survive like aquarium plants do, but aquarium lighting is nevertheless important in fish aquariums too - for one thing, fish aquariums are often planted with real plants too, and for another, lighting gives the fish their natural day-night rhythm. In addition, the right light ensures good colours for your ornamental fish in the aquarium.

Modern aquarium lighting now almost exclusively uses energy-saving LEDs. You can find out all about this aquarium lighting in our blog "LED lighting in aquaristics.

Nice to have

This aquarium technology makes your life easier, but is not absolutely necessary to run a successful fish aquarium:

• UV clarifier: reduces germs and algae spores in the open water.
• Automatic feeder: Automatically doses the fish food and thus allows you to go on holiday without an aquarium.
• CO2 system: Only for heavily planted fish aquariums! CO2 is a plant fertiliser, fish exhale CO2 and don't do anything with the substance in the water.
• Aquarium cooler: An aquarium cooler makes sense in particularly hot summers; it prevents the aquarium temperature from rising too high and the fish from getting oxygen problems.

Is it absolutely necessary to plant the aquarium?

A clear YES to this. Real plants in the aquarium can contribute to a very favourable aquarium climate. They reduce the risk of algae infestations, consume pollutants such as nitrate and phosphate from the aquarium water and release vital oxygen into the water that your fish breathe.

Nevertheless, there are various fish aquariums that (have to) manage without plants at all - mostly because the fish would simply eat the plants, and because in nature they also live in biotopes without plants. An example of this are cichlids from the African lakes Tanganyika and Malawi. Some loricariids are also very hungry for plants and will not leave anything green in the aquarium.

In these special cases, the filtration has to get the pollutants out of the water that the plants would normally take care of, and you have to make sure that enough oxygen gets into the aquarium even without aquarium plants by adjusting the filter flow or using an air stone.

Which substrate should I choose?

In a fish aquarium, there is usually gravel or sand at the bottom of the aquarium. Brown leaves, larger rock slabs and smaller pebbles can also be used. Here you should be guided by what the substrate looks like in the biotopes your fish come from.

If in doubt, you can't go wrong with a fine, rounded aquarium gravel. The aquarium plants can root well here, and the rounded gravel grains mean that the risk of injury is low even if your fish actively burrow into the substrate.

Different shapes of fish aquariums

In the trade we usually have rectangular aquariums, panorama aquariums with curved front glass and cube-shaped cubes. They are all basically suitable for keeping fish.

Round or cylindrical aquariums such as the notorious goldfish bowl, on the other hand, are unsuitable for keeping fish; fish can experience severe stress here because the strongly curved walls send their own swimming movements as signals to their lateral line organ, thus making them believe the permanent presence of predators. These aquarium forms are not permitted for keeping fish in Germany.

Hexagonal tanks and other more exotic aquarium shapes have also never really caught on in fishkeeping.

So which aquarium shape should I choose for which fish?

• Cubes: Cube tanks are usually somewhat smaller and are mainly suitable for very small fish species or for fish that do not swim much. The Siamese fighting fish, for example, is an ideal candidate for a cube from about 20 litres.
• Standard rectangular aquariums: These are suitable for the vast majority of aquarium fish, including those that like to swim longer distances. For these fish (many tetras are among them), choose an edge length that allows them to stretch their fins.
• Scaper's tanks: These aquariums have a smaller height compared to the base area and are actually intended for aquascapers, but they are also super suitable for keeping bottom-dwelling fish such as loricariids or armoured catfish.

Popular types of fish aquariums

Here we present the most popular types of fish aquariums that can be found in living rooms and fish cellars at home.

The community aquarium

In a community aquarium, fish are kept that are well matched in terms of their requirements for water values, temperature, food and aquarium size. As a rule, a community aquarium is planted and decorated with roots and stones, which give the fish in the tank structure and hiding places. In a typical community aquarium, no attention is paid to things like a common origin among the fish. What is allowed is what fits together in terms of requirements and is pleasing.

Typically, fish in a community aquarium are often selected according to water zones: Depending on the size of the aquarium, one or two bottom fish such as catfish and armoured catfish, and one or two fish species that live in the middle and upper water zones, such as guppies or platies, tetras and danios.

The species tank

For fish with more specific requirements, keeping them in a species tank is a good idea. Here you can cater exactly to the needs of your fin-finned friends and set up the aquarium just the way they want it. Typical candidates for a species tank are some loricariids, but also South American cichlids, fighting fish or gobies - although in principle you can keep any aquarium fish in a species tank!

The biotope aquarium

In a biotope aquarium you orientate yourself on the natural habitats of the fish you want to keep here. You only use aquarium plants that also occur in nature in the biotope of the fish, and only mix fish and invertebrates that also live together in the natural habitats.